Alloy castings, including those made from aluminum, magnesium, and iron, often house aircraft generator components which are subject to stringent design requirements and rigorous environmental operating conditions. In order to provide resistance and prevent corrosion against oil and other solvents inherent with the operation of aircraft generator components, alloy castings are often treated and sealed with an organic coating such as resin. A resin seal provides a physical barrier for the alloy casting against the hot oil and other solvents necessary for the generator components to function effectively.
One procedure for sealing resin to a housing made from a cast alloy material includes dipping the housing in a phenolic resin bath in which an aromatic solvent has been combined with a phenolic resin. After immersion, any excess dripping resin is wiped off before the housing is baked in an oven. During baking, the aromatic solvent evaporates leaving a seal of cured phenolic resin. With such a crude procedure, however, critical dimensions which are crucial to an aircraft generator's performance are difficult to obtain; and, intensive labor is required in attempting to meet such critical dimensions. This added time and effort directly effects the cost associated with manufacturing alloy castings. In addition, this procedure employs the use of aromatic solvents which are known for their environmentally unfriendly impact on the ozone layer, and whose use may soon be severely curtailed by United States governmental regulations.
The desirability of an epoxy resin coating curing agent is addressed in U.S. Pat. No. 5,204,385 to Naderhoff. The Naderhoff patent teaches a water reducible epoxy curing agent which is prepared by first reacting a chemical excess of a polyfunctional epoxide compound with a quaternary ammonium salt, and then, condensing the unreacted epoxide groups of the reaction product with a polyamine. While the Naderhoff patent addresses the particular chemistry of an epoxy resin curing agent, it does not, as the invention to be described more fully hereinafter, detail a method of how to seal resin to an alloy casting, especially in circumstances when dimensions are critical to meet.
A process for producing flat products from particulate material is disclosed in a patent to Bellis et al, U.S. Pat. No. 4,772,322. The process comprises the steps of: forming a relatively smooth cartable slurry, comprising a suspension of particulate material in an aqueous solution, a film-forming binder material and a dispersion of a particulate synthetic resin in an aqueous solution; depositing a coating of this slurry onto a support surface; and heating the deposited coating to a temperature at which a component of the synthetic resin volatilizes. The Belles et al patent, however, does not, as the invention to be described more fully hereinafter, provide a method for sealing resin to an alloy casting; rather, the patent utilizes a resin curing agent to manufacture a product by curing a resin particulate coating on a metallic substrate, and then, specifically separates the shaped coating from the substrate as a flat product. Thus, the Belles et al patent employs the coating as the finished formed product.
A process and composition which produces a permanently water wadable, abrasion-resistant film on a surface is disclosed in a patent to Rickert, Jr., U.S. Pat. No. 4,536,420. In the process, a composition, comprising a mixture of an aqueous colloidal dispersion of carboxylic acid functional polymer, an aqueous colloidal dispersion of surface hydroxylated silica, an amine to render the carboxylic acid functional polymer water soluble, a curing agent for the carboxylic acid functional polymer, and a wetting agent, is applied to a surface to form a film, and the film is dried and/or heated at a temperature sufficient to harden or cure the film. While the Rickert, Jr. patent addresses a process of applying a film to a surface, the chemistry of the composition applied is directed to that of an acrylic resin. The chemistry of such a composition is completely different from an epoxy or phenolic resin which is present with the instant invention. Further, the Rickert, Jr. patent is specifically directed to producing a water wadable surface, while the instant invention is directed to a method of sealing resin to a surface to form a physical barrier between a solvent such as oil and an alloy casting.
The present invention is directed to overcoming one or more of the above problems.